1. Field of the Invention
This invention relates generally to information processing apparatus and, more particularly, is directed to word processing apparatus for processing information having different character and line pitches.
2. Description of the Prior Art
Word processing apparatus which are adapted to edit typed characters and words displayed on the screen of a CRT (cathode ray tube or Braun tube) and type out such edited characters and words by means of an electrically controllable typewriter or other printing apparatus, are well known in the art. Generally, in such apparatus, character information is stored in a memory of the apparatus as character code data. When it is desired to display the information on the screen of the CRT, the character code data is sequentially read out from the memory in synchronism with the scanning operation by the CRT, converted by a character generator to dot data representing characters to be displayed, and such dot data is then supplied to the CRT, whereupon the characters are displayed on the screen thereof. Various editing operations can then be performed on the character information displayed by the CRT.
Because of the increase in complexity of information to be processed, it may be required to display information having different line pitches, that is, different spacings between the lines in the vertical direction on the screen of the CRT. In order to vary the line pitch, however, complicated hardware is generally required.
It may further be required to view information that is to be amended or changed in, for example, a vertical scroll operation, while simultaneously viewing stationary or non-changing information. If two CRTs are used for the two types of information, it is to be appreciated that the manufacturing costs and space occupied by the CRTs become prohibitive. Therefore, it is desirable to divide a single CRT screen into a plurality of areas or sections for independently displaying information in each area. Thus, for example, information in an upper section of the screen can be vertically scrolled while information in a lower section of the screen remains stationary. However, the control of information in two areas becomes extremely complicated, particularly where different line pitches are mixed within the two areas.
Another problem that results is that when information having different line pitches is simultaneously displayed on, for example, an upper section of a CRT screen, the dividing line between the upper and lower sections on the screen may intersect the last line displayed on the upper portion. It is therefore known to move the dividing line in the vertical direction to either delete the last line in its entirety or include the last line in its entirety. This method, however, may be undesirable from the viewpoint of providing hardware to perform such function. Further, such movement of the dividing line may change the information displayed on the lower portion of the screen. It is therefore desirable to maintain the dividing line at the same position, while also preventing the aforementioned problem of the dividing line intersecting the last line on the upper portion of the screen.